Prior transmitters and transceivers, insofar as known to Applicant, have not had means for disabling the transmission mode while switching channels. This has made possible spurious transmissions by operators who hold down the transmit switch, or push-to-talk microphone switch, and at the same time switch transmission frequencies. Because of the possibility of simultaneously changing channels and transmitting, the FCC regulations, at Section 96.58(c) (2) state that: "Multi-frequency transmitters shall not provide more than 23 transmitting frequencies, and the frequency selector shall be limited to a single control." Thus, acceptable Class D Citizens Band transmitters and transceivers have been limited to one frequency selector control.
However, in many instances it is desirable to provide more than one frequency selector control for a given transmitter or transceiver. For example, in a mobile installation, the microphone is typically hand held in use by the vehicle driver as he drives the vehicle, and the transmitter or transceiver itself is typically remote from the driver, typically being installed on or near the dashboard of the vehicle. With the one frequency selector control conventionally located on the front panel of the transceiver itself, it is at least inconvenient (and may be unsafe) for the operator to simultaneously drive the vehicle, handle the microphone and attempt to manipulate the channel selector control on the transceiver front panel.
Further, with only a single channel selector control, a given transceiver cannot alternatively be used with a microphone having a channel changing capability and other microphones, such as desk types or addendums such as remote or plug-in type voice operated units, which do not have their own channel selection capability but rather require location of the channel selector on the front panel of the transmitter or transceiver itself.
Accordingly, the objects and purposes of this invention include provision of:
A radio apparatus as aforesaid, and particularly a transmitter or transceiver, such as of the Class D Citizens Band type, wherein simultaneous transmission and switching of channels is precluded.
Apparatus, as aforesaid, which precludes undesirable or impermissible radio interference caused by running the carrier from frequency to frequency with the transmitter in transmit mode either with or without modulation, and which further precludes "keying" of the transmitter or transceiver by holding down the transmitter "on" switch and switching the frequency selector in and out of the desired frequency.
Apparatus, as aforesaid, which renders permissible the provision of more than one frequency selector control in a Class D Citizens Band transmitter or transceiver by precluding operating of the transmitter while switching transmission frequencies.
Apparatus, as aforesaid, which at least for convenience permits a given transmitter or transceiver system to incorporate both a microphone-mounted frequency selector and a transmitter or transceiver front panel-mounted frequency selection control, and particularly in mobile use enhances both driving safety and flexibility in mounting of the transmitter or transceiver unit.
Apparatus, as aforesaid, wherein a microphone provided with a frequency selector control can be unplugged and removed to prevent unauthorized transmission by a transceiver, while still permitting use of the receiver portion and selection among several crystal controlled reception channels.
Apparatus, as aforesaid, wherein a transmitter or transceiver may be utilized with a variety of microphones or other voice sources, whether or not such sources include a channel selector control.
Apparatus, as aforesaid, in which prevention of simultaneous transmission and frequency selection is readily achievable in otherwise conventional transmitters and transceivers, with only minimal additional circuitry or change and at a minimal cost and is achievable in a variety of transmitter types.
Other objects and purposes of this invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.